Method, transmission unit, system and computer program for wireless communication between a camera and at least one remote flash device

ABSTRACT

The present invention generally relates to the field of communication between electronic devices used for photography. In particular, the invention relates to a method, transmission unit, system and computer program for wireless communication between a camera and at least one remote flash device, such as photoflash units and related equipment. More in particular, the invention provides a way of controlling a plurality of flash devices from an intermediate radio transmission unit mountable on the camera, and utilized a delay a sequence flash control sequence so as to synchronize the function of the camera and the remote flash devices during image acquisition. Further the invention provides a way of controlling in the photoflash units settings for the main flash, wherein the setting are the last settings determined by the camera when the intermediate radio transmission unit was in a TTL-mode.

TECHNICAL FIELD

The present invention generally relates to the field of communicationbetween electronic devices used for photography. In particular, theinvention relates to a method, transmission unit, system and computerprogram for wireless communication between a camera and at least oneremote flash device, such as photoflash units and related equipment.

BACKGROUND ART

Photoflash units, also called flash devices, flash lighting devices etc,of various kinds are commonly used in photography for producing a flashof artificial light to help illuminate a scene, a scene which wouldotherwise be perceived as underexposed, i.e. too dark, to the viewer ofa captured picture of the scene. Other uses of flashes are capturingquickly moving objects or changing the quality of light. Most currentflash lighting devices are electronic and have been developed throughxenon-based flash devices to state of the art light emitting diode (LED)flash devices. Historically, flashes were produced by means of ratherinconvenient arrangements, such as single-use flashbulbs and flammablepowders. As a contrast to these historical arrangements, modern camerasoften activate connected flash lighting devices automatically, and therapid technological development of compact pocket cameras, mobileterminals and smart phones has nowadays led to relatively advanced,in-built cameras with very high resolution and adaptable flash devicesas a de facto standard with few exceptions.

In order to utilize various commonly used flash lighting devices, camerabodies are according to internationally accepted standards equipped witha so-called hot shoe accessory connector. A flash lighting device may beconnected, directly or through an extension cord, to the hot shoeconnector. The emission of flash light from the lighting device can besynchronized to an image acquisition by the camera by a synchronizationsignal received by the lighting device. In prior art camera systems,this synchronization signal is transmitted from the camera to the flashdevice via its connection to the hot shoe connector.

In modern applications of camera systems and in studio equipment forphotography, a remote flash lighting device can be triggered by wirelesssynchronization, which has been realized using optical, such asinfrared, and radio frequency communications to the remote flash device.Radio frequency synchronization typically involves connecting a radiotransmitter to the camera body and a radio receiver to the remote flashdevice. The radio transmitter sends a signal to the radio receiver toactivate the remote flash device in synchronization with imageacquisition by the camera. For that purpose, radio frequencycommunication systems may include a transmitter at the remote flashdevice for sending a confirmation signal back to the camera side radio,indicating that the flash-side radio has successfully activated theflash lighting device in use.

In order for such two-way communication in a camera system to be fullyfunctional and reliable, it is necessary for the camera and for theflash device to comply with standards available. Also their respectiveexternal or integrated modules for the execution of communication therebetween, need to be compatible and to support existing standards withrespect to signalling schemes that are in use by different camera andflash device manufacturers on the market. Since standardizationavailable in the field is allowing for deviations with respect tocertain more advanced functions, both mechanically and electronically,it is in practice hard or even impossible to satisfy all requirements ifcomplete operability is requested.

Through-the-lens (TTL) flash photographic control typically involves thecamera body measuring lighting conditions, such as an amount of energyin the form of light, provided by a flash lighting device during a testfiring or preflash of the flash device. The measurement is performedthrough the lens of the camera. The camera then provides an indicationto the flash device connected to the hot shoe connector of the amount oflight, i.e. provision of power and timing, to be applied by a main flashduring the actual image acquisition procedure. The indication of theamount of light can be made by providing start and stop signals to theflash device via the hot shoe connector.

In another example of TTL flash photographic control, the indication ofthe amount of light can be made by providing a serial data, via the hotshoe connector to the flash device connected thereto, that includes anadjustment to the amount of light that was provided in the preflash. Theflash device in the hot shoe connector can activate a remote flash lightby utilizing optical flash pulses, such as visible light or infraredlight. The optical pulses can also be used to send TTL power adjustmentsto the remote flash device. However, according to this control system,the remote lighting devices are not providing any information back tothe flash lighting device in the hot shoe connector of the camera body.This system therefore requires that a light emitting device be connectedto the hot shoe connector.

Using camera and flash or similar lighting systems presently availableon the market means that the choice of camera in practice limits thechoice of flash device or related lighting device, or alternatively, inthe sense that a flash or lighting device limits the choice of camera.Each manufacturer of cameras advocates its own specific communicationprotocol for communication with flash devices intended for use with thatparticular camera. For an amateur photographer who is in possession of aflash device, which cannot be used any longer together with certaincamera equipment because of the above mentioned limitation, this may begreatly discouraging. For a professional photographer, or a commercialstudio environment collaborating with many different photographers withvarying preferences in their choice of camera equipment, this may be asevere limitation. To overcome the limitation, professional studios aretypically obliged to be equipped with numerous brands of flash devices,so as to accommodate the needs of any professional photographer, and asa consequence the costs to the studio are substantially increased.

Another problem when using flash or similar lighting systems presentlyavailable on the market is that is can in some situations be hard todetermine if TTL-mode or manual mode should be used. In manual mode thepower level is set manually. Both TTL-modes and manual mode have theirstrengths and shortcomings. One mode is not always better than theother. Many photographers often switch between TTL-mode and manual-modedepending upon the situation of the shoot.

There have been made attempts to overcome the mentioned problem. Flashlighting devices have been available that allow for mechanicalsubstitution of the part in contact with the hot shoe connector of thecamera. However, having to modify the lighting devices to be used tovarious camera bodies is highly undesired. In addition to that, there isno way of overcoming the limitation that use of numerous lightingdevices together with one camera is impossible, unless all lightingdevices are produced by the same vendor and thus are recommended andfully compatible with the camera equipment in use. When consideration ismade to a standard type of studio environment, lighting devices ofdifferent types and brands are often hinged near the ceiling of thestudio and therefore in practice impossible to adjust or substitutecomponents on, only to be usable together with various cameras.

It is therefore conceivable to assume that a market incentive exists toremove the mentioned limitations one way or the other. However, despitethis incentive, and despite prior attempts to overcome problems relatingto the limited choice of equipment due to lacking interoperability,there is presently no solution available. It would seem logical todevelop and introduce to the market flash devices that are able tosimultaneously operate with a variety of different camera types andbrands. No such flash devices have yet been developed.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to alleviate theabove limitations. This object is attained by a method for controllingsettings of at least one remote flash device and for synchronizing itsfunction to image acquisition of a camera, using an intermediate radiotransmission unit for wireless transmission of radio signals to theremote flash device and for bi-directionally exchanging signals with thecamera via a physical connection between the intermediate radiotransmission unit and the camera. The method comprising the steps of:switching the intermediate radio transmission unit from a TTL-mode,Through-the-lens, to a manual mode; transmitting from the camera via theintermediate radio transmission unit to the remote flash device, a mainflash activation signal; applying in the remote flash device settingsfor the main flash, wherein the setting are the last settings determinedby the camera when the intermediate radio transmission unit was in aTTL-mode.

One of the main advantages of the present invention is that the solutionreduces the problem that it is in some situation hard manually set thepower level of the remote flash device manually. This since after theintermediate radio transmission unit has been switched from TTL-mode,Through-the-lens, to a manual mode the remote flash device applies thelast settings for the main flash determined by the camera when theintermediate radio transmission unit was in a TTL-mode. The photographercan therefore start out the process of manually set the power of theremote flash device from the setting determined when the intermediateradio transmission unit was in a TTL-mode. The process to manually setthe power therefore becomes quicker any easier for the photographer.

Another advantage of the present invention is that the inventioneliminates the problem of proprietary communication protocols limitingphotographers and professional studios to the use of only flash devicesof the same brand as their camera equipment, due to lackinginteroperability between camera systems from different producers. Bymeans of the present invention, the signalling from the intermediateradio transmission unit is standardized to the greatest extent possible,in order to enable communication with a wide range of available remoteflash devices, high end models and more average ones, modern andrelatively old ones.

Another significant advantage of the present invention is that allsignals exchanged between the camera and the remote flash devices, i.e.transmission of information and commands related to the functionality ofthe remote flash devices, are transmitted from the camera via theintermediate radio transmission unit to remote flash devices in itscontrol. No signaling goes from the remote flash devices in use back tointermediate radio transmission unit or to the camera, which simplifiesthe process and makes it possible for the camera to control not onlyone, but a plurality of remote flash devices and related equipment. Theinvention is operable without overly complicating the signaling orrequiring confirmation messages to be sent from the remote flash devicesvia the intermediate radio transmission unit and back to the camera.

The present invention provides a way of utilizing available industrialstandards relating to communication interfaces for signaling betweendevices of a camera system. Thus, by limiting signaling and commandsfrom the intermediate radio transmission unit to generic portions ofproprietary communication interface protocols of different camera andflash device producers, compatibility between devices is achieved. Thisis aspect of the present invention, gives the photographer a wider rangeof options by making photographic devices interoperable betweendifferent brands.

In accordance with another aspect of the present invention, theintermediate radio transmission unit is attached to the hot shoeconnector of the camera. The transmission from the intermediate radiotransmission unit is wireless, typically within the ordinary radiofrequency range, and thus the need to place a flash device in hot shoeconnector on the camera is replaced by the intermediate radiotransmission unit, which provides a more versatile and flexiblesolution. This is a way of obtaining a functional TTL control systemwithout having to attach the flash device to the hot shoe connector ofthe camera is highly beneficial to studio photographers in particular.

In accordance with yet another aspect of the present invention, anaspect which is realized in a further embodiment of the invention,adaptation is made of operational properties of the intermediate radiotransmission unit to corresponding operational properties of the camerato which it is connected. The operational properties of the intermediateradio transmission unit may then relate to the signaling scheme used forcommunication with the connected camera. As previously mentioned, allcameras are not able to communicate with all flash devices. Therefore,by adapting the intermediate radio transmission unit, possibly byaltering its signaling scheme to the commanding camera, whilesimultaneously maintaining the standardized interface towards the remoteflash devices in use, interactivity between various comprised units in acamera system having digital TTL functionality commanding a remote flashdevice system is obtained.

In accordance with another embodiment of the present invention, theremote flash device uses an in-built flash radio receiver unit forcommunicating with the intermediate radio transmission unit. Also use ofan external receiver means for receiving information and commands fromthe intermediate radio transmission unit is a possible realization ofthe invention. By using modules for the communication between devices,compatibility between different brands, models and production years isensured, and so is a way for new producers of communication devices foruse in the field of photography to enter into the market and competewith the already established producers.

In yet another embodiment of the invention, an indication that theremote flash device is either unavailable or available, is realized bysetting a clock signal in its low or high state, respectively. This isrealized in a manner to utilize to the maximum already existingfunctionality in the intermediate radio transmission unit, so as toavoid unnecessary complexity and additional costs to the end customers.This clock signal may also be replaced by an acknowledge signal from theintermediate transmission unit, possibly delayed for a certain timeperiod so as to effect the timing of the camera. This because the cameramay need to await the acknowledgement signal as a confirmation, beforeit initiates action of some kind.

According to one of the more important aspects of the present invention,the wireless transmission realized by the intermediate radiotransmission unit enables all necessary communication without the needto attach flash devices physically to the hot shoe connector of thecamera. The remote flash device may thus comprise a plurality of unitsforming an arrangement that is capable of managing a wide variety ofdifferent lighting conditions during image acquisition.

The present invention therefore enables complete functionality of thecamera and a remote flash device system of any kind, so as to obtain anoptimal quality of captured images during a photographic session.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, advantages and effects as well as features of the inventionwill be more readily understood from the following detailed descriptionof exemplary embodiments of the invention when read together with theaccompanying drawings, in which:

FIG. 1 schematically illustrates a camera system according to anexemplary embodiment of the present invention, the system comprising acamera, an intermediate radio transmission unit and a plurality of flashdevices controlled by the camera.

FIG. 2 illustrates a signaling scheme of digital TTL flash photographiccontrol according to an exemplary embodiment of the present invention.

FIG. 3 illustrates a flow chart of the method for wireless communicationaccording to an exemplary embodiment of the present invention.

FIG. 4 illustrates a signaling scheme of digital TTL flash photographiccontrol according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

Throughout this document, the term flash refers either to the flash oflight itself or to the electronic flash unit discharging the light.

Through-the-lens (TTL) flash photographic control originally appeared inabout 1980 in analogue form and has later been transformed into digitalTTL, which is even more accurate also allows for more advancedfunctionality. The main features of digital TTL are that prior to theactual exposure and the firing of the main flash, one or more smallflashes called preflashes are emitted. The light returning through thelens is measured and this value is used to calculate the amount of lightnecessary for the actual exposure. Multiple preflashes can be used toimprove the flash output. Canon refers to this technique as “E-TTL” andhas recently improved the system with a new generation “E-TTL II”. Thefirst form of digital TTL by Nikon, called “D-TTL”, was originallyintroduced, and since then, the superior “i-TTL” system has beenpromoted. From a user's perspective, the two digital TTL versions E-TTLand i-TTL are unfortunately incompatible, at least with respect to moreadvanced functionality, of which all modern digital flash controlsystems are full.

When using front-curtain flash, i.e. when the flash fires immediatelyafter the shutter opens, the preflashes and main flash appear as one tothe human eye, since there is very little time between them. When usingrear-curtain flash, i.e. when the flash fires at the end of theexposure, and a slow shutter speed, the distinction between the mainflash and the preflashes is more obvious.

Different cameras and flash units are naturally associated withdifferent specifications and performance, depending on model, intendedmarket segment and production year. Some cameras and flash units takemore information into account when calculating the necessary flashoutput, including the distance of the subject to the lens. This improvesthe lighting when a subject is placed in front of a background, inparticular when the background is substantially darker than the subjectto the lens. If the lens is focused on the subject, the flash will becontrolled to allow for proper exposure on the subject, thus leaving thedarker background underexposed. Alternatively, if the lens is focused onthe background, the background will be properly exposed, leaving thesubject in the foreground typically overexposed. This technique requiresboth a camera capable of calculating the distance information, as wellas the lens being capable of communicating the focal distance to thebody.

More advanced TTL flash techniques include off-camera flash lighting,where one or more flash units are located at different locations aroundthe subject. In this case a so-called commander unit, which can beintegrated in the camera body, is used to control all of the remoteunits. The commander unit usually controls the remote flashes by usingflashes of visible or infrared light. The photographer can normally varythe light ratios between the different flashes. However, as mentioned,the lacking interoperability between brands and models is still alimitation that has not yet been completely circumvented, at least notin a way that is satisfying to stakeholders like photographers andstudios.

With particular reference to FIG. 1, a schematic picture illustrates acamera system according to an exemplary embodiment of the presentinvention. The system includes a camera 110 with a lens 120 andobjective. The camera is equipped with a hot shoe connector 150, onwhich an intermediate radio transmission unit 130 is attached. Anantenna 140 of the intermediate transmission unit is shown, from whichsignals are transmitted to be received by a corresponding receiverantenna 180 on a remote flash device 160 having a transparent window 170from which the actual flash light is to be illuminated.

When a camera is used in conjunction with a photoflash unit, thephotoflash unit can fail to fire, depending upon a variety of causes.Possible causes include a failure of the camera itself or the photoflashunit, poor electrical contact at the connection between the two, and thesignals transferred to the photoflash unit for firing being improper.

The international standard ISA 10330:2002(E) specifies electricalrequirements of a camera synchronizer, an ignition circuit in aphotoflash unit and a cable to connect these comprised units in ageneral photoflash system. Of course, the cable may be exchanged with awireless transmission system without departing from the scope of thestandard, which is also directed towards test specification of methodsto secure positive firing of the photoflash unit.

Referring to FIGS. 2 and 3, a signaling scheme and a flow chartaccording to an exemplary embodiment of the present invention aredisplayed. Signals are exchanged between the three main constituentscomprised, the camera, the intermediate radio transmission unit and oneremote flash device 160, in wireless control and to which a plurality ofremote flash devices 160 can be added. The sequence begins in that thecamera transmits to the intermediate radio transmission unit a preflashactivation signal 301. Thereafter, the intermediate radio transmissionunit starts a timer 303 causing a delay, which delay together with asubsequent time period for forwarding the preflash activation signal tothe remote flash device 160 and another subsequent time period for theremote flash device 160 to receive and transform the preflash activationsignal into emission of light energy, constitutes a compound delay ofthe mentioned three different time periods. This compound delay isvariable in that the timer delay is adjustable. Adaptation is thus madeso as to let the compound delay coincide in time with a predetermineddelay between the point in time when the camera transmits the preflashactivation signal and the point in time when the camera initiates apreflash image analysis 307.

This adaptation therefore enables the preflash image analysis 307 tooccur in synchronization with the preflash. This has the effect that thecamera acts as if it has a flash device attached to its hot shoeconnector, but instead of the flash device, a transmitter is attached tothe camera and this transmitter controls a number of remote flashdevices 160 in synchronization with the digital TTL functionality of thecamera.

In dependence on the preflash image analysis, the camera determinessettings 308 to be applied during a subsequent main flash, andtransmits, via the intermediate radio transmission unit to the remoteflash device 160, the determined settings 309 for the remote flashdevice 160 to apply during the main flash, and transmits, also via theintermediate radio transmission unit to the remote flash device 160, amain flash activation signal 310 upon which the main flash and imageacquisition occurs.

Information about the predetermined delay can be retrieved from thecamera, from a memory associated to the camera or to the intermediateradio transmission unit, It can also be determined through a testsequence, whereby the intermediate radio transceiver unit runs a testcycle so as to obtain the time in which light is captured during thepreflash image analysis.

FIG. 4 illustrate a signaling diagram for another exemplary embodimentof the present invention. This exemplary embodiment can be combined withthe previously described embodiments. The embodiment assumes that atleast one cycle of the exemplary embodiments described in relation toFIGS. 3 and 4 has been completed. That is that settings has beendetermined by the camera 110 and transmitted from the camera 110 to theintermediate radio transmission unit 130. As in the previously describedembodiments are signals exchanged between the three main constituentscomprised, the camera, the intermediate radio transmission unit and oneremote flash device 160, in wireless control and to which a plurality ofremote flash devices 160 can be added. The sequence begins in that theintermediate radio transmission unit 130 is switched from a TTL-mode toa manual mode, in a step 410. Manual mode of the intermediate radiotransmission unit 130 is a mode in which the flash power of the flash orflashes in the system can be manually set to a desired value. If e.g. abrighter image is desired the power of the flash light from the flash orflashes in the system is increased. Switching the intermediate radiotransmission unit 130 from the TTL-mode to the manual mode can be donein many different ways, e.g. by actuating a switch or a knob on theintermediate radio transmission unit 130 or by selecting manual mode ina user interface of the intermediate radio transmission unit 130.Thereafter, in a step 420 is a main flash activation signal transmittedfrom the camera 110 via the intermediate radio transmission unit 130 tothe remote flash device 160. In the next step 430, the remote flashdevice 160 applies the settings for the main flash, wherein the settingare the last settings determined by the camera 110 when the intermediateradio transmission unit 130 was in a TTL-mode. Since the remote flashdevice 160 applies the last settings determined by the camera 110 whenthe intermediate radio transmission unit 130 was in a TTL-mode the firstimage acquired in manual mode is an image with correct exposure. Anadvantage with using the last setting in TTL-mode is that it is easierand faster to also obtain a desired exposure in manual mode since onlyadjustments of the flash power are necessary instead of starting with anunknown value of the flash power.

In an exemplary embodiment of the method described above the settings inthe step of applying are retrieved in the remote flash device 160 from amemory in the remote flash device 160. The setting are the last settingpreviously received from the camera 110 via the intermediate radiotransmission unit 130 when the intermediate radio transmission unit 130was in a TTL-mode. In this exemplary embodiment, where the settings areretrieved in the remote flash device 160 from a memory in the remoteflash device 160, when the flash power is changed in the intermediateradio transmission unit 130 a change value is transmitted from theintermediate radio transmission unit 130 to the remote flash device 160,the change value represents an increase or decrease of the desired flashpower.

In another exemplary embodiment of the method described above thesetting in the step of applying are transmitted from the intermediateradio transmission unit 130 to the remote flash device 160, the settingare the last setting previously received from the camera 110 via thephysical connection when the intermediate radio transmission unit 130was in a TTL-mode. In this exemplary embodiment when the flash power ischanged in the intermediate radio transmission unit 130 a change valueis transmitted from the intermediate radio transmission unit 130 to theremote flash device 160, the change value represents an absolute vale ofthe flash power, wherein the absolute value is calculate based on theflash setting stored in the intermediate remote device and a desiredchange of flash power that is inputted by a user.

In the exemplary embodiments described in relation to FIG. 4 there is noneed for a preflash and subsequent measurement by the camera since theintermediate radio transmission unit 130 is in manual mode.

Now referring back to FIGS. 2 and 3, these figures can also be used toillustrate a signaling diagram for another exemplary embodiment of thepresent invention. This exemplary embodiment can be combined with thepreviously described embodiments. In this exemplary embodiment of thepresent invention it is possible to adjust a power relation betweenremote flash devices in the system. This adjustment can in an exemplaryembodiment of the present invention be made in the intermediate radiotransmission unit. For instance if there are two flashes in the systemit can be set in the intermediate radio transmission unit that the firstflash should emit a flash with twice as much power as the first flash.As in the previously described embodiments are signals exchanged betweenthe three main constituents comprised, the camera, the intermediateradio transmission unit and one remote flash device, in wireless controland to which a plurality of remote flash devices can be added. Thesequence begins in that the camera transmits to the intermediate radiotransmission unit a preflash activation signal 301. Thereafter, theintermediate radio transmission unit starts a timer 303 causing a delay,which delay together with a subsequent time period for forwarding thepreflash activation signal to the remote flash device and anothersubsequent time period for the remote flash device to receive andtransform the preflash activation signal into emission of light energy,constitutes a compound delay of the mentioned three different timeperiods. However in this exemplary embodiment the preflash activationsignal can also contains information about the amount of power that thedifferent flashes should use for their respective preflash. The amountof power for the different preflashes from the respective flashcorresponds to the power relation for the main flashes from thedifferent flashes. If for instance a user has set that the main flashfrom the first flash should contain twice as much power as the powerfrom the second flash the preflash from the first flash should also betwice as powerful compared to with the preflash from the second flash.The amount of power for the preflashses for the respective flashes canalso be transmitted from the intermediate transmission unit before apreflash activation signal 301 is transmitted. The amount of power forthe respective preflashes from the different flashes are then stored inthe respective flashes.

As in the previously described exemplary embodiments the compound delayis variable in that the timer delay is adjustable. Adaptation is thusmade so as to let the compound delay coincide in time with apredetermined delay between the point in time when the camera transmitsthe preflash activation signal and the point in time when the camerainitiates a preflash image analysis 307.

This adaptation therefore enables the preflash image analysis 307 tooccur in synchronization with all the preflashes from the different theremote flash device 160. This has the effect that the camera acts as ifit has a flash device attached to its hot shoe connector, but instead ofthe flash device, a transmitter is attached to the camera and thistransmitter controls a number of remote flash devices in synchronizationwith the digital TTL functionality of the camera.

In dependence on the preflash image analysis of the preflashes from theseveral remote flash devices 160 the camera determines settings 308 tobe applied during a subsequent main flash, and transmits, via theintermediate radio transmission unit to the remote flash devices 160,the determined settings 309 for the remote flash devices 160 to applyduring the main flash. In this exemplary embodiment of the presentinvention the camera determines settings 308 to be applied during asubsequent main flash from the different remote flashes 160 based ondifferent amount of power in the preflashes from the respective remoteflash devices 160. The camera is not aware of how many remote flashdevices 160 that are used and neither that the different flashes usedifferent power in the preflashes from the different flashes. Thesettings therefore only constitute one value to be applied during asubsequent main flash. In an exemplary embodiment the setting 309 is anindication if the power from the remote flash devices 160 should beincrease or decrease, and with how much the power should be increased ordecreased. For instance if the camera determined that the light from thedifferent preflashes is not enough for a correct exposure, the setting309 will be an indication to increase the power from the remote flashdevice 160 with a certain amount. And if the camera determined that thelight from the different preflashes is to power full for a correctexposure, the setting 309 will be an indication to decrease the powerfrom the remote flash device 160 with a certain amount. Thereafter thecamera also transmits, via the intermediate radio transmission unit tothe remote flash device, a main flash activation signal 310 upon whichthe main flashes from the different remote flashes 160 occur and imageacquisition occurs.

Information about the predetermined delay can be retrieved from thecamera, from a memory associated to the camera or to the intermediateradio transmission unit, It can also be determined through a testsequence, whereby the intermediate radio transceiver unit runs a testcycle so as to obtain the time in which light is captured during thepreflash image analysis.

One of the definitions used in flash photography is the synchronizer orsynchronizing means. By this is meant a device provided in a camera orshutter unit, which fires the photoflash unit in synchronization withthe operation of the camera shutter, and which comprises synchronizerterminals, a synchronization switch and an electronic circuit thatconnects the two.

Polarities of the synchronizer terminals in a camera and that of theignition circuit terminals in a photoflash unit coupled with the cameraare predefined. The polarity of the synchronizer terminals shall bematched to that of the ignition circuit terminals in the coupledphotoflash unit. The construction of the present invention is alignedwith such requirements so as to be applicable with known internationalstandard interfaces.

For the camera accessory shoe with electrical contacts, which iscommonly designated the hot shoe connector of the camera, and for thefoot of photoflash equipment with electrical contacts, which is commonlydesignated foot of the flash device, positive, negative and/or groundedpoles and their relative potentials are predefined. Also the geometry ofthe hot shoe and the foot are predetermined, which is a requirement forinteroperability of different cameras and flash devices. However,additional poles and connection points may have been arranged bydifferent camera or flash producers so as to allow for addedfunctionality, which goes beyond the standardized functions andrequirements. As a result of this practice of adding connection pointsthat are adapted to governing the additional functions, and despite theinternational standardization efforts, interoperability of differentbrands of camera models and flash equipment is lost. Some functions ofmore simple nature may still work, but the broad range of additionalfunctions, necessary at least for a professional photographer are nolonger possible to utilize, unless the camera and related flash deviceand other equipment are perfectly matched.

The detailed description is of the best mode presently contemplated forpracticing the present invention. It is not intended to be taken in alimiting sense, but is made merely for the purpose of describing generalprinciples. The scope of the invention is to be ascertained withreference to the issued claims.

1-15. (canceled)
 16. A method for adjusting a power relation between aplurality of different remote flash devices using through-the-lens (TTL)flash control and an intermediate radio transmission unit for wirelesstransmission of radio signals to the remote flash devices and forbi-directionally exchanging signals with a camera via a physicalconnection between the intermediate radio transmission unit and thecamera, the method comprising the steps of: receiving information orsetting by the respective remote flash devices the amount of power thatthe remote flash devices should use for their respective preflashes;receiving by the respective remote flash devices a preflash activationsignal received from the camera via the intermediate radio transmissionunit; emitting at the same point in time from the respective remoteflash devices preflashes with a power relation according to the receivedinformation or setting received by the remote flash devices, wherein thepower relation is adjusted between the plurality of different remoteflash devices using through-the-lens (TTL) flash control; receiving bythe remote flash devices one common amplification based on thepreflashses to be applied during subsequent main flashes from all of thedifferent remote flash devices, said one common amplification from thecamera via the intermediate radio transmission unit; receiving by theremote flash devices a main flash activation signal from the camera viathe intermediate radio transmission unit; applying in the remote flashdevices the one common amplification to the power for the respectivepreflashes; and emitting at the same point in time from the respectiveremote flash devices main flashes with a power relation corresponding tothe power relation for the preflashes.
 17. The method according to claim16, wherein the information or setting received by the respective remoteflash devices about the amount of power that the remote flash devicesshould use for their respective preflash are set in the intermediateradio transmission unit.
 18. The method according to claim 16, whereinthe information or setting received by the respective remote flashdevices about the amount of power that the remote flash devices shoulduse for their respective preflash are transmitted in the preflashactivation signal.
 19. The method according to claim 16, wherein theinformation or setting received by the respective remote flash devicesabout the amount of power that the remote flash devices should use fortheir respective preflash are transmitted before the preflash activationsignal.
 20. The method according to claim 16, wherein the setting forthe remote flash devices to apply during the main flash is an indicationif the power from the remote flash devices should be increased ordecreased, and with how much the power should be increased or decreased.21. The method according to claim 16, wherein a preflash image analysisis made to determine settings relating to the amount of light energyrequired for exposure of an image acquisition in present lightingconditions.
 22. The method according to claim 16, wherein a remote flashdevice uses an in-built flash radio receiver unit for receiving signalsfrom the intermediate radio transmission unit.
 23. A non-transitorycomputer readable medium having a program stored thereon for executing acomputer to perform the method in accordance with claim
 16. 24. Themethod according to claim 16, wherein the amount of power that each ofthe remote flash devices should use for their respective preflashes isdifferent.
 25. The method according to claim 16, wherein the informationor setting in the respective remote flash devices of the amount of powerthat the remote flash devices should use for their respective preflashesvaries.
 26. A method performed in an intermediate radio transmissionunit for adjusting a power relation between a plurality of differentremote flash devices using through-the-lens (TTL) flash control, themethod comprising the steps of: transmitting information to therespective remote flash devices corresponding to different amounts ofpower for their respective preflashes; receiving from a camera apreflash activation signal; transmitting the preflash activation signalto the respective remote flash devices preflashes for emission with apower relation according to the information transmitted to therespective remote flash devices, wherein the power relation is adjustedbetween the plurality of different remote flash devices at least in partusing through-the-lens (TTL) flash control; transmitting one commonamplification to be applied during subsequent main flashes to all of thedifferent remote flash devices, said one common amplification beingreceived from the camera; and transmitting to the remote flash devices amain flash activation signal received from the camera.
 27. The methodaccording to claim 26, wherein the information transmitted to therespective remote flash devices corresponding to the different amountsof power of their respective preflashes varies.
 28. The method accordingto claim 26 wherein the intermediate radio transmission unit ismountable in a hot shoe connector of the camera.
 29. The methodaccording to claim 26, wherein a confirmation signal is transmitted tothe camera indicating that a remote flash device is momentarilyunavailable, the indication being realized by setting a clock signal ofthe intermediate radio transmission unit in its low state.
 30. Themethod according to claim 26, wherein an availability signal istransmitted to the camera indicating that a remote flash device isavailable, the indication being realized by setting a clock signal ofthe intermediate radio transmission unit in its high state.
 31. Themethod according to claim 26, wherein the intermediate radiotransmission unit is adaptable to operational properties of the camerato which it is connected.
 32. The method according to claim 31, whereinoperational properties of the intermediate radio transmission unitrelate to physical properties and/or a communication interface of thecamera to which the unit is connected.
 33. The method according to claim26, wherein the information transmitted to the remote flash devices forthe respective preflashes is previously determined by the camera in athrough-the-lens mode of the intermediate radio transmission unit. 34.The method according to claim 33, wherein the steps in claim 1 areperformed with the intermediate radio transmission unit in a manual modeafter the step in claim 18 is performed with the intermediate radiotransmission unit in the through-the-lens mode.
 35. Intermediate radiotransmission unit for wireless transmission of radio signals to severalremote flash devices and for bi-directionally exchanging signals with acamera via a physical connection between the intermediate radiotransmission unit and the camera, the intermediate radio transmissionunit being adapted to control settings of several remote flash devicesand to synchronize its function to image acquisition of the camera inaccordance with the method of claim
 26. 36. A camera system forcontrolling settings of at least one remote flash device and forsynchronizing its function to image acquisition of a camera, the camerasystem including the intermediate radio transmission unit in accordancewith claim 35, and being adapted to control settings of the remote flashdevice and to synchronize its function to image acquisition of thecamera in accordance with the method.
 37. A method for through-the-lens,TTL, control of a plurality of different remote flash devices, saidmethod comprising the steps of: receiving by the different remote flashdevices respective inputs indicating amounts of power that the differentremote flash devices should use for preflashes, wherein the plurality ofdifferent remote flash devices are controlled at least in part viathrough-the-lens, TTL, control; emitting at the same point in time fromthe different remote flash devices preflashes with different powersaccording to the received respective inputs; and receiving by thedifferent remote flash devices one common amplification relating to theamount of light energy required from the different remote flash devicesfor exposure of an image acquisition in present preflash lightingconditions based on the preflashes emitted with the amounts of power asindicated by the respective inputs.
 38. The method according to claim37, further comprising the steps of: applying in the remote flashdevices the one common amplification to the power for the respectivepreflashes; and emitting at the same point in time from the respectiveremote flash devices main flashes with a power relation corresponding tothe power relation for the preflashes.
 39. A method performed in anintermediate radio transmission unit for through-the-lens, TTL, controlof a plurality of different remote flash devices, said method comprisingthe steps of: transmitting to the different remote flash devicesrespective inputs indicating amounts of power that the different remoteflash devices should use for the preflashes, wherein the plurality ofdifferent remote flash devices are controlled at least in part viathrough-the-lens, TTL, control; transmitting to the remote flash devicesan activation signal for emitting at the same point in time from thedifferent remote flash devices preflashes with different powersaccording to the respective inputs; and transmitting to the differentremote flash devices one common amplification relating to the amount oflight energy required from the different remote flash devices forexposure of an image acquisition in present preflash lighting conditionsbased on the preflashes emitted with the amounts of power as indicatedby the respective inputs.
 40. The method according to claim 39, furthercomprising a step of: transmitting to the remote flash devices a mainflash activation signal for emitting at the same point in time from therespective remote flash devices main flashes with the one commonamplification.